See this article - we cover that here: Creating a Mail List Sign Up Component for the Experience Manager Toy Store Site
The reason why I pointed you to this article is because you wanted to know why @SlingServlet did not work.
An important aspect to notice is the change on how an AEM Servlet is created. There is no longer @Service or @SlingServlet annotations in the org.osgi.service.component.annotations package.
In Maven Archetype 10 project, you defined a servlet like this:
@SlingServlet(paths="/bin/mySearchServlet", methods = "POST", metatype=true)
public class HandleClaim extends org.apache.sling.api.servlets.SlingAllMethodsServlet {
private static final long serialVersionUID = 2598426539166789515L;
However, in a Maven Archetype 11 project., you define an AEM Servlet like this (there is no @SlingServlet annotation):
@Component(service=Servlet.class,
property={
Constants.SERVICE_DESCRIPTION + "=Simple Demo Servlet",
"sling.servlet.methods=" + HttpConstants.METHOD_POST,
"sling.servlet.paths="+ "/bin/myDataSourcePoolServlet"
})